GB2640869A - A turbomachine, and thermofluid systems comprising the same - Google Patents

Abstract

A turbomachine 1, such as a turbine, pump or compressor, comprises a housing 2 enclosing a chamber 3, and a hollow shaft 4 rotatably mounted to the housing, at least a first part of the hollow shaft being within the chamber and comprising one or more first holes 5a, 5b, 5c in an elongate wall 4a of the hollow shaft. One or more discs 6 within the chamber are affixed to the at least first part of the hollow shaft. One or more second holes 7 within the housing allow a working fluid to enter or exit the chamber in a direction that is substantially orthogonal to the axis of the hollow shaft and substantially tangential to the direction of rotation of the disc(s). A rotor within the hollow shaft may be affixed to a secondary shaft that is rotatably mounted to the hollow shaft. Spacers may be disposed on one or both planar surfaces of the one or more discs to reduce vibrations and direct the working fluid. Each spacer may be proximate to an outer perimeter of a disc and may span an entirety of its planar surface in a radial direction such that the working fluid is directed along one or more curvilinear paths extending in the radial direction.

Description

A TURBOMACHINE, AND THERMOFLUID SYSTEMS COMPRISING THE

SAME

FIELD OF THE INVENTION

The present invention relates to turbomachines, and thermofluid systems comprising the same.

BACKGROUND

Thermofluid systems such as engines, refrigerators, and heat pumps typically convert heat energy into mechanical energy or vice versa. Turbomachines such as turbines, compressors and pumps typically form part of some such thermofluid systems. Turbines achieve the aforementioned energy conversion process by converting some of the pressure, heat and kinetic energy, that is, enthalpy, of a working fluid into mechanical energy in the form of shaft rotation, that is, shaft power. Conversely, compressors and pumps convert some of the shaft power into an enthalpy increase in the working fluid.

Persons skilled in the art of thermofluid systems will appreciate the ongoing desire to improve the efficiency with which such energy conversion processes are carried out. This is especially apparent in light of the ever-growing desire for less carbon-intensive methods of power generation and consumption.

Similarly motivated to improve the efficiency of turbomachines, Nikola Tesla invented a type of turbine which exploited the so-called "boundary-layer effect" exhibited by flowing fluids when in contact with a solid surface (first discovered by Ludwig Prandtl). Tesla's turbine comprises one or more discs affixed to a rotatable shaft and enclosed in a housing. Person skilled in the art of thermofluid systems know how Tesla's turbine is operated, and so such operation will be omitted here for the sake of brevity.

It should be noted, however, that one or more holes are present proximate to the centre of each disc of Tesla's turbine. These holes enable working fluid to exit the housing after it has imparted/spent the majority of its momentum onto the discs, and thereby make way for the upstream working fluid entering the housing. However, these holes constitute a significant source of loss/inefficiency in Tesla's turbine. Firstly, in order to flow axially through the holes and exit the housing, the spent fluid has to undergo a significant change in direction from a swirling/spiralling direction to an axial one. Secondly, the now axially-flowing spent fluid is able to interact and interfere with downstream working fluid that is acting/working on other (surfaces of the) disc(s). Thirdly, the discs' holes are in themselves acting as baffles, increasing the tortuosity of the path which the axially-flowing spent fluid must take to exit the housing.

All of this results in a central portion of the discs being placed in contact with turbulent and generally axially-flowing fluid, thus reducing the proportions of the discs' surfaces which are able to generate shaft power via the boundary-layer effect.

The present invention seeks to mitigate or alleviate the aforementioned issues.

SUMMARY OF INVENTION

In a first aspect, a turbomachine is provided in claim 1.

In another aspect, a thermofluid system is provided in claim 7.

In yet another aspect, another thermofluid system is provided in claim 10.

Further respective aspects and features of the invention are defined in the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 schematically illustrates a turbomachine according to embodiments of the present invention; * Figure 2 schematically illustrates a turbomachine according to embodiments of the present invention; * Figure 3 schematically illustrates a disc of a turbomachine according to embodiments of the present invention; * Figure 4 schematically illustrates a turbomachine according to embodiments of the present invention; * Figures 5A-5B schematically illustrate turbomachines according to embodiments of the present invention; * Figures 6A-6C schematically illustrate discs of a turbomachine according to embodiments of the present invention; and * Figure 7 schematically illustrates a turbomachine according to embodiments of the present invention.

DETAILED DESCRIPTION

A turbomachine, and thermofluid systems comprising the same are disclosed. In the following description, a number of specific details are presented in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to a person skilled in the art that these specific details need not be employed to practice the present invention. Conversely, specific details known to the person skilled in the art are omitted for the purposes of clarity where appropriate.

Turning now to Figure 1, in embodiments of the present invention, a turbomachine 1 comprises a housing 2 enclosing a chamber 3; a hollow shaft 4 rotatably mounted to housing 3, wherein at least a first part of hollow shaft 4 is within chamber 3, wherein the first part of hollow shaft 4 comprises one or more first holes 5a, 5b, 5c in an elongate wall 4a of hollow shaft 4; one or more discs 6 within chamber 3 and affixed to the at least first part of hollow shaft 4; and one or more second holes 7 within housing 2, wherein the one or more second holes 7 are configured such that, when in use, a working fluid enters or exits the chamber in a direction that is substantially orthogonal to the axis of the hollow shaft and is substantially tangential with respect to the direction of rotation of the discs.

As mentioned previously, significant losses arise in Tesla's turbine due to generation of turbulence around the shaft, with the holes in the discs being the main cause of this turbulence generation.

The inventor has found that these issues may be alleviated or mitigated by providing hollow shaft 4 containing one or more holes 5a, 5b, 5c in its elongate wall 4a, as opposed to having holes in the discs (as does Tesla's turbine). As will be appreciated by persons skilled in the art, this hollow shaft provides a separate chamber into which spent fluid may enter radially (via the holes) after having spiralled along the surface of the discs. Once in this separate chamber, the spent fluid can exit the housing axially.

By separating the working fluid spiralling along the discs (thereby rotating the discs) from the spent fluid into two different chambers, the interaction and interference between arising between the two can be minimised, thereby reducing the amount of turbulence generated in the working fluid within chamber 3.

Moreover, whatever turbulence is generated in the spent fluid (due to passing through the shaft's holes and/or by changes in flow direction from spiralling to axial) is contained within the hollow shaft rather than in the central region of the discs, thereby allowing a greater proportion of the discs' surfaces to be able to generate shaft power via the boundary-layer effect.

As mentioned previously, turbomachine 1 may be a turbine, compressor, pump or the like. Moreover, turbomachine 1 may typically be found within a thermofluid system such as an engine, refrigerator or heat pump or the like, and its role within such thermofluid systems may typically involve the conversion of a working fluid's enthalpy into shaft power, or vice versa.

Housing 2 provides an enclosed space (that is, chamber 3) in which disc(s) 6 may reside. As will be appreciated, by placing disc(s) 6 within chamber 3 (that is, the enclosed space formed by housing 2), disc(s) 6 may be protected from collisions with foreign objects and debris, and/or adverse ambient conditions such as rain or hail, for example.

Moreover, by placing disc(s) 6 within chamber 3, a more effective use of the working fluid may be achieved, as chamber 3 ensures that respective parts of the working fluid contact both surfaces of each disc 6, and also that the amount of time the working fluid is in contact with the surfaces of the disc(s) 6 is sufficient for the working fluid to impart the majority of its momentum onto the discs.

Housing 2 comprises one or more second holes 7. Second hole(s) 7 may be of any shape/cross-section the skilled person deems appropriate. However, the orientations and/or positions of second hole(s) 7 within housing 2 contribute to the resulting fluid flow path arising within chamber 3 when the turbomachine is in use.

Turning now to Figure 2, which is a cross-section view of section A-A depicted in Figure 1, it can be seen that the orientation and/or position of second hole 7 within housing 2 relative to disc(s) 6 and/or hollow shaft 4 may be such that the axis of second hole 7 is oriented in a substantially orthogonal direction to the axis of hollow shaft 4 (coming out of the page in Figure 2), and is oriented in a substantially tangential direction to the direction of rotation of disc(s) 6 (depicted as a black curved arrow in Figure 2). As will be appreciated, by having the axis of second hole 7 oriented in such a manner, working fluid entering or exiting the chamber via second hole 7 will be directed in a similar orientation. Therefore, an inwardly-spiralling path is likely to be formed by the working fluid after it enters chamber 3 via second hole 7, that is, when turbomachine 1 is being operated in a similar manner to that of Tesla's turbine (hereafter referred to as "a Tesla turbine").

Other factors contributing to this inwardly-spiralling path being adopted by the working fluid include the working fluid being enclosed within chamber 3 and the working fluid losing its momentum due to the viscous forces in the boundary layer formed on the discs decelerating the working fluid. This fluid path is advantageous in that the amount of time the working fluid is in contact with the disc surface is maximised, thereby maximising the length of the boundary layer formed, and thus the amount of viscous forces generated on the disc, leading to an increased shaft power being generated.

Conversely, when turbomachine 1 is being operated similarly to a Tesla compressor/pump (that is, in the opposite manner to that of a Tesla turbine), the combined effect of housing 2 enclosing the working fluid within chamber 3, the rotation of disc(s) 6, and the orientation/positioning of second hole(s) 7 causes the working fluid entering chamber 2) via first hole(s) 5a, 5b, 5c in the at least first part of hollow shaft 4) to take on an outwardly-spiralling path towards second hole(s) 7. This fluid path is advantageous in that the amount of time the working fluid is in contact with the disc surface is maximised, thereby maximising the length of the boundary layer formed, and thus the amount of viscous forces generated on (and so momentum imparted to) the fluid. This results in an increased amount of working fluid compression, and thus a greater enthalpy increase in the working fluid.

Hence more generally, second hole(s) 7 of housing 2 may be configured (that is, positioned and/or oriented) such that, when in use, a working fluid enters or exits the chamber in a direction that is substantially orthogonal to the axis of the hollow shaft and is substantially tangential with respect to the direction of rotation of the discs.

Hollow shaft 4 is rotatably mounted to housing 2. This is to say that hollow shaft is attached/mounted to housing in such a manner so as to permit the rotation of hollow shaft 4. As will be appreciated, hollow shaft 4 should be allowed to rotate in order that shaft power be generated when turbomachine 1 is operated like a Tesla turbine, or consumed when turbomachine 1 is operated like a Tesla compressor/pump.

As will be appreciated, the present invention is not limited to the type of means employed for enabling hollow shaft 4 to be rotatably mounted to housing 2.

Examples of such means 8 may take the form of bearings, a gearbox, the application of oil, grease or lubricant onto the contacting portions of hollow shaft 4 and housing 2 or the like, or indeed any combination of the preceding.

At least a first part of hollow shaft 4 is contained within housing 2. Turning back to Figure 1, this first part may be thought of as the part of hollow shaft 4 which lies to the right of the section A-A line. As will be appreciated, having this first part (or indeed the entirety of hollow shaft 4) within the housing enables the disc(s) 6, which are contained within chamber 3, to be affixed to hollow shaft 4. By affixing the disc(s) 6 to (the at least first part of) hollow shaft 4, rotation of the disc(s) 6 may cause the rotation of hollow shaft 4, or vice versa. This is to say that the rotation of disc(s) 6 is translated into shaft power, or vice versa, due to the connection between disc(s) 6 and hollow shaft 4.

The at least first part of hollow shaft 4 comprises one or more first holes 5a, 5b 5c in elongate wall 4a of hollow shaft 4. Elongate wall 4a of hollow shaft 4 may be thought of as the wall which extends in the axial direction of hollow shaft 4. As will be appreciated, the first hole(s) 5a, 5b, 5c may be of any shape/cross-section the skilled person deems appropriate.

In particular, it will be appreciated that a given first hole 5a may extend underneath one of discs 6 affixed to the at least first part of hollow shaft 4. This may be advantageous in that a shorter/more direct/less tortuous fluid path is provided between the surface of disc 6 and the interior of hollow shaft 4, thereby further reducing the amount of turbulence generated by spent fluid as it exits chamber 3 (in the case of turbomachine 1 being operated like a Tesla turbine), or by working fluid as it enters chamber 3 (in the case of turbomachine 1 being operated like a Tesla compressor/pump).

Alternatively or in addition, a given first hole 5b may extend underneath a plurality (or all) of discs 6. Doing so may provide the aforementioned advantages of first hole 5a, but may also provide the further advantage of simplifying manufacture of hollow shaft 4, as fewer holes which extend underneath discs 6 may be required.

This becomes increasingly apparent as the number of discs 6 used in turbomachine 1 increases.

Alternatively or in addition, a given first hole 5c may extend between two of discs 6, or between one of disc(s) 6 and the housing 2. This is to say that a given first hole 5c may be placed in a region of elongate wall 4a that is not in contact with any of disc(s) 6. First hole 5c may extend (in an axial direction) across a part or entirety of such a region of elongate wall 4a.

In any case, when turbomachine 1 is operated like a Tesla turbine, first hole(s) 5a, 5b, 5c permit spent fluid to exit chamber 3 and enter the interior of hollow shaft 4, which thus minimises the amount of interaction and interference arising between working fluid and spent fluid, thereby reducing the amount of turbulence generated within the working fluid residing in chamber 3. Conversely, when turbomachine 1 is operated like a Tesla compressor/pump, the low-enthalpy fluid may enter axially through the interior of hollow shaft 4, and thus undergo a direction change in a separate region/chamber prior to being exposed to rotating disc(s) 6 within chamber 3, thereby also reducing the amount of turbulence generated within the fluid residing chamber 3.

One or more discs 6 are contained within the chamber and affixed to the at least first part of hollow shaft 4. As can be seen in Figure 1, disc(s) 6 maybe axially aligned with respect to each other and hollow shaft 4, and may be spaced apart along elongate wall 4a of hollow shaft 4. While disc(s) 6 have been depicted as having a circular outer perimeter in Figure 2, disc(s) 6 may be of any shape/size that the skilled person deems appropriate. For example, a given disc 6 may have a polygonal or elliptical outer perimeter.

As mentioned previously, affixing the disc(s) 6 to (the at least first part of) hollow shaft 4 results in rotation of the discs causing the rotation of hollow shaft 4, or vice versa. This is to say that the rotation of disc(s) 6 is translated into shaft power, or vice versa, due to the connection between disc(s) 6 and hollow shaft 4.

As will be appreciated, the present invention is not limited to the type of means employed for affixing disc(s) 6 to the at least first part of hollow shaft 4. Examples of such means may take the form of adhesives, fixings (such as nuts and bolts, screws, rivets or the like), welding, machining/additively manufacturing disc(s) 6 and hollow shaft 4 as one monolithic part, or the like.

As with a Tesla turbine or a Tesla compressor/pump, the spacings of disc(s) 6 between each other and the interior walls of housing 2 is ideally such that no region of inviscid (that is, one-dimensional) fluid flow arises between the opposing planar surfaces of two neighbouring discs 6 or the opposing planar surface of a disc 6 and an interior wall of housing 2. This is because such an inviscid flow region cannot be used to exert viscous forces onto disc 6 -no boundary layer is present within such inviscid flow regions (also known as freestream regions).

Regarding boundary layers, it will be appreciated that either a laminar or turbulent boundary layer may arise along the planar surfaces of disc(s) 6. In the case of a turbulent boundary layer arising along the planar surfaces, such boundary layers should not be seen as being a source of loss/inefficiency in the turbine, as such boundary layers typically possess a predictable structure (comprising a viscous sublayer, buffer layer, and log-law layer), and typically have an overall directionality to them (in this case a spiralling direction). Such features distinguish turbulent boundary layers from the turbulent flows the present invention aims to reduce/eliminate, which are typically unpredictable in structure and have a less well-defined directionality to them.

For the avoidance of doubt, a planar surface of a disc 6 is the surface lying in a plane that is substantially orthogonal to the axis of hollow shaft 4. Figure 2 depicts the planar surface of disc 6.

During operation of turbomachine 1, disc(s) 6 may experience high rotational velocities, typically in the order of thousands of revolutions per minute (rpm). Such high rotational velocities may result in disc(s) 6 being fatigue damaged due to any resulting vibrations generated by the rotation of disc(s) 6. For example, any imbalance in the centre of mass of a given disc 6 or hollow shaft 4 with respect to the axis of rotation is likely to result in large unbalanced centripetal forces acting on the disc(s) 6, such centripetal forces being proportional to the square of rotational velocity.

To alleviate or mitigate this issue, and turning now to Figure 3, one or more 30 spacers 9 may be disposed on one or both planar surfaces of one or more of disc(s) 6. As can be seen in Figure 3, a given spacer 9 may be disposed at any location on a given planar surface of a given disc 6. For example, a given spacer 9 may be disposed proximate (that is, closer) to an inner perimeter 6a of a given disc, or proximate to an outer perimeter 6b thereof, or at a midpoint between inner perimeter 6a and outer perimeter 6b.

Turning now to Figure 4, it can be seen that when the disc(s) 6 are affixed to the at least first part of hollow shaft 4, spacer(s) 9 may contact the opposing planar surfaces of two neighbouring discs 6, or may contact a planar surface of a disc 6 and an interior wall of housing 2. Through such contact, spacers 9 may provide additional structural rigidity/stiffness to disc(s) 6, thus reducing the amplitude of vibrations experienced by the disc(s) 6 during use. Optionally, spacers 9 may be (partly) made of a damping material to provide additional vibration amplitude reduction in the form of damping, that is, vibrational energy absorption.

For a given spacer 9 making contact with an interior wall of housing 2, it may be beneficial that such spacer 9 be (partly) made of a material with a low coefficient of friction such as graphite or polytetrafluoroethylene (PTFE). This is because such spacer 9 is moving relative to the interior wall of housing 2 while making contact therewith, which may result in frictional forces being generated, resulting in losses/inefficiencies in the conversion of enthalpy to shaft power, or vice versa.

By using a material with a low coefficient of friction, the amount of such losses may be reduced.

As will be appreciated, while spacer(s) 9 may aid in reducing vibrations experienced by disc(s) 6, they may act to disturb the flow of working fluid over the planar surfaces of disc(s) 6, leading to turbulence being generated along the planar surfaces. To alleviate or mitigate this issue, spacer(s) 9 may be shaped and oriented (and optionally sized) so as to minimise their disturbance to the flow of working fluid along the planar surfaces of disc(s) 6, and even guide the flow in the aforementioned spiralling pathways.

Turning back to Figure 3, it can be seen that spacer(s) 9 may have a generally streamlined (for example, teardrop/crescent) shape so as to minimise the size of the wake (and thus the amount of turbulence) generated by spacer(s) 9. Moreover, spacer(s) 9 may be oriented so as to turn/guide working fluid towards inner perimeters 6a of disc(s) 6 as disc(s) 6 rotate anti-clockwise when operated like a Tesla turbine, or turn/guide compressed fluid towards second hole(s) 7 as disc(s) 6 rotate clockwise when operated like a Tesla compressor/pump. Persons skilled person in the art will appreciate that spacer(s) 9 may be shaped and oriented to enable such turning/guiding of the fluid using the opposite rotation directions. This is to say that embodiments of the present invention are not limited to the direction in which disc(s) 6 rotate.

Optionally, a given spacer 9 may be sized such that it spans a minor portion of the respective planar surface of a given disc 6 in both a radial and azimuthal direction thereof. Turning back to Figure 4, it can be seen that each spacer 9 spans the minority of the distance between inner perimeter 6a and outer perimeter 6b, and the sector formed between the centre of disc 6 and the foremost and aftmost points of spacer 9 (see dashed line in Figure 4), spans the minority of the area enclosed by outer perimeter 6b. In this way, the amount of and/or extent to which working fluid is disturbed may be reduced, thereby reducing the amount of turbulence generated along the planar surface of disc(s) 6.

In any case, it will be appreciated that more generally, in embodiments of the present invention, one or more of disc(s) 6 may optionally each have one or more spacers 9 disposed on one or both planar surfaces of disc 6, wherein the one or more spacers 9 are configured to reduce vibrations experienced by the discs and direct the working fluid when in use.

Optionally, at least one of spacer(s) 9 may be disposed proximate to outer perimeter 6b of the respective disc 6. This may be beneficial in that the amount of turbulence generated along the planar surfaces of disc(s) 6 may be reduced.

For example, when turbomachine 1 is operated like a Tesla turbine, turbulence may be generated within the working fluid as it enters chamber 3 via second hole(s) 7, and so outer perimeter 6b of disc(s) 6 may be in contact with turbulent working fluid. A similar region of turbulent fluid arises around outer perimeter 6b when turbomachine 1 is operated like a Tesla compressor/pump, with turbulence being generated within the compressed fluid as it exits second hole(s) 7.

By positioning a given spacer 9 proximate to outer perimeter 6b, then the resulting disturbance to the working fluid may be reduced, as the fluid flow is already turbulent at this location. Conversely, by positioning a given spacer 9 at a midpoint between inner and outer perimeters 6a, 6b, or proximate to inner perimeter 6a, the laminar (or at least less turbulent) working fluid in these regions is likely to experience a significant disturbance, thus generating greater levels of turbulence along the planar surface of the disc. To use an analogy, shouting at a festival typically has less impact than shouting at a library.

As will be appreciated, when turbomachine 1 is in use, fluid flows arise within the interior of hollow shaft 4. It may be beneficial to make use of such fluid flows in order to convert a greater amount of enthalpy into shaft power or vice versa, thereby increasing the efficiency of turbomachine 1.

Turning now to Figures 5A and 5B, embodiments of the present invention may optionally comprise a rotor 10a, 10b within hollow shaft 4. In such embodiments, rotor 10a, 10b may be used to convert some of the enthalpy of the spent fluid entering the interior of hollow shaft 4 via first hole(s) 5a, 5b, 5c into shaft power when turbomachine 1 is operated like a Tesla turbine, or may be used to convert some of the supplied shaft power into an enthalpy increase in the low-enthalpy fluid as it exits hollow shaft 4 via first hole(s) 5a, 5b, 5c when turbomachine 1 is operated like a Tesla compressor pump.

As will be appreciated, a rotor (such as rotor 10a, 10b) may be thought of as a part of a machine (such as turbomachine 1) that rotates about an axis when the machine is in use. Thus, rotor 10a, 10b may be mounted to the interior of hollow shaft 4 such that rotor 10a, 10b may rotate when turbomachine 1 is in use. This rotation of rotor 10a, 10b enables the aforementioned energy conversion processes to be carried out.

Preferably, rotor 10a, 10b comprises one or more vanes/blades. This is because vaned/bladed rotors are typically more efficient than vaneless/bladeless rotors (such as disc(s) 6) at converting enthalpy to shaft power (or vice versa) when the working fluid is flowing axially or is flowing in a radial-to-axial/axial-to-radial path.

Conversely, and as found by Tesla, disc(s) 6 are typically more efficient than vaned/bladed rotors at converting enthalpy to shaft power (or vice versa) when the working fluid is flowing in an azimuthal/circumferential direction, as is the case with the inwardly-and outwardly-spiralling paths discussed previously.

Turning to Figure 5A, rotor 10a may be mounted within the interior of hollow shaft 4 such that at least part of rotor 10a intersects the axis of at least one of first hole(s) 5a, 5b, 5c. In this case, the distance through which fluid travels axially between rotor 10a and first hole(s) 5a, 5b, 5c may be minimised, thereby minimising the amount of turbulence generated between disc(s) 6 and rotor 10a. Turbulence arising in this region may impact the efficiency of whichever of disc(s) 6 and rotor 10a is downstream of the other when turbomachine 1 is in use.

Preferably, rotor 10a may be a radial flow rotor such as those found in commonly-known centrifugal compressors/pumps and/or radial turbines, details of which being omitted from the present description for the sake of brevity. Having a radial flow rotor as rotor 10a may be beneficial in that they are typically designed to efficiently convert the enthalpy of working fluid flowing radially into shaft power while simultaneously turning the working fluid towards an axial direction, or convert shaft power into an enthalpy increase in working fluid flowing axially while simultaneously turning the working fluid towards a radial direction. This is to say that a radial flow rotor may carry out an efficient energy conversion in the region of turbomachine 1 at which fluid follows a radial-to-axial or axial-to-radial path (between the interior of hollow shaft 4 and first hole(s) 5a, 5b, 5c, for example).

Turning to Figure 5B, rotor 10b may be mounted within the interior of hollow shaft 4 such that rotor 10b does not intersect any of the axes of first hole(s) 5a, 5b, 5c. Given the previous discussion regarding the generation of turbulence between the rotor and disc(s) 6, guiding element 11 may optionally be disposed within the interior of hollow shaft 4 such that it reduces the volume of the interior of the at least first part of hollow shaft 4. As can be seen in Figure 5B, guiding element 11 forms an annular channel within the interior of the at least first part of hollow shaft 4, thereby reducing the volume thereof By reducing the volume in this way, the amount to which the fluid may expand (and thus generate turbulence) may be reduced.

Guiding element 11 may be of any shape/cross-section the skilled person deems appropriate, provided that such guiding element 11 enables the aforementioned volume reduction. Moreover, it will be appreciated that guiding element 11 (if employed) may be used as (part of) the means by which rotor 10b is mounted to the interior of hollow shaft 4.

Preferably, rotor 10b may be an axial flow rotor such as those found in commonly-known turbojet and turbofan engines, details of which being omitted from the present description for the sake of brevity. Having an axial flow rotor as rotor 10b may be beneficial in that they are typically designed to efficiently convert the enthalpy of working fluid flowing axially into shaft power, or vice versa. This is to say that an axial flow rotor may carry out an efficient energy conversion in the region of turbomachine 1 at which fluid follows an axial path (along the interior of hollow shaft 4, for example).

Rotor 10a, 10b may optionally be affixed to the interior of (that is, within) hollow shaft 4 such that rotation of hollow shaft 4 results in rotation of rotor 10a, 10b. Due to this affixation, the disc(s) 6 and rotor 10a, 10b may rotate at the same rotational velocity when turbomachine 1 is in use. As will be appreciated, the present invention is not limited to the type of means employed for affixing rotor 10a, 10b to the interior of (that is, within) hollow shaft 4. Examples of such means may take the form of adhesives, fixings (such as nuts and bolts, screws, rivets or the like), welding, machining/additively manufacturing rotor 10a, 10b and hollow shaft 4 as one monolithic part, or the like. As mentioned previously, if the rotor used is rotor 10b, then guiding element 11 may be as (part of) the means by which rotor 10b is affixed to the interior of hollow shaft 4.

Preferably, rotor 10a, 10b may be affixed to a secondary shaft (not shown) that is rotatably mounted to hollow shaft 4. Rotor 10a, 10b may thus rotate at a different rotational velocity to that of hollow shaft 4 when turbomachine 1 is in use, as the secondary shaft to which rotor 10a, 10b is affixed is able to rotate independently from hollow shaft 4. This may enable a more efficient energy conversion within turbomachine 1 when in use, as rotor 10a, 10b may rotate at its optimal rotational velocity and disc(s) 6 may operate at their optimal rotational velocity (which is typically higher than that of rotor 10a, 10b).

Preferably, the secondary shaft may be coaxial with hollow shaft 4, that is, hollow shaft 4 and the secondary shaft may be arranged as pair of concentric shafts. The pair of concentric shafts may optionally be geared together via a gearbox such that rotation of hollow shaft 4 causes rotation of the secondary shaft at a different rate, or vice versa. This may make subsequent use of generated shaft power (or the consumption of provided shaft power) simpler, as only one of the shafts require connection to other components of a thermofluid system to enable both shafts to rotate when in use.

Alternatively, the pair of concentric shafts may be allowed to rotate entirely independently of each other to ensure that each shaft (and so each of rotor 10a, 10b and disc(s) 6) rotate at their respective optimal rates for the specific operating conditions turbomachine 1 may be subjected to (fluid flow rates/temperature/pressure, ambient temperature/pressure/humidity, and the like).

As will be appreciated, the present invention is not limited to the type of means employed for affixing rotor 10a, 10b to the secondary shaft. Examples of such means may take the form of adhesives, fixings (such as nuts and bolts, screws, rivets, or the like), welding, machining/additively manufacturing rotor 10a, 10b and the secondary shaft as one monolithic part, or the like. Additionally, the present invention is not limited to the type of means employed for enabling the secondary shaft to be rotatably mounted to hollow shaft 4. Examples of such means may take the form of bearings, a gearbox (as mentioned previously), the application of oil, grease or lubricant onto the contacting portions of hollow shaft 4 and the secondary shaft or the like, or indeed any combination of the preceding. If the rotor used is rotor 10b, then guiding element 11 may be as (part of) the means by which the secondary shaft may be rotatably mounted to hollow shaft 4.

As mentioned previously, turbomachine 1 may be operated like a Tesla turbine (to 5 convert enthalpy into shaft power) or may be operated like a Tesla compressor/pump (to convert shaft into an enthalpy increase). Such modes of operation will now be described below, Turbomachine 1 may be used as part of a thermofluid system. As mentioned previously, examples of thermofluid systems include engines, refrigerators and heat pumps. Further examples include hydroelectric turbines, pumps for transporting fluids, air conditioners, ventilation systems or the like. Additionally, a thermofluid system may comprise a combination of any preceding example. In any case, it will be appreciated that in embodiments of the present invention, a thermofluid system may comprise one or more turbomachines 1.

Moreover, in embodiments of the present invention, one or more of turbomachines 1 within the thermofluid system may be configured to operate like Tesla compressor/pumps. This is to say that one or more of turbomachines 1 may be configured such that, when in use: hollow shaft 4 rotates, thereby causing disc(s) 6 to rotates; the working (in this case, low-enthalpy) fluid enters chamber 3 via (the interior of) hollow shaft 4 and first hole(s) 5a, 5b, 5c; the rotation of disc(s) 6 compresses the working fluid due to the boundary-layer effect; and the compressed (that is, high-enthalpy) working fluid exits chamber 3 via second hole(s) 7. As will be appreciated, this method of operation is analogous to that of operating a Tesla compressor/pump in that the low-enthalpy fluid is let into turbomachine 1 axially, enters chamber 3 proximate to the inner perimeter 6a of disc(s) 6, and exits chamber 3 tangentially to the direction of rotation of disc(s) 6, as is the case with a Tesla compressor/pump.

Where embodiments of the present invention comprise rotor 10a, 10b affixed to/ geared with hollow shaft 4, then it will be appreciated that rotation of hollow shaft 4 causes rotation of rotor 10a, 10b, resulting in low-enthalpy fluid being compressed by rotor 10a, 10b before entering chamber via second hole(s) 7. Where embodiments of the present invention comprise rotor 10a, 10b affixed to an independently rotating secondary shaft, then it will be appreciated that to achieve the aforementioned compression using rotor 10a, 10b, the secondary shaft may be rotated separately from the rotating of hollow shaft 4.

Alternatively or in addition, one or more of turbomachines 1 within the thermofluid system may be configured to operate like Tesla turbines. This is to say that one or more of turbomachines 1 may be configured such that, when in use: the working (in this case, high-enthalpy) fluid enter chamber 3 via second hole(s) 7; the working fluid rotates disc(s) 6 due to the boundary-layer effect; thereby causing hollow shaft 4 to rotate (that is, generated shaft power); the (now spent/lowenthalpy) working fluid exits chamber 3 via first hole(s) 5a, 5b, 5c and (the interior of) hollow shaft 4. As will be appreciated, this method of operation is analogous to that of operating a Tesla turbine in that the high-enthalpy fluid is let into turbomachine 1 tangentially to the rotation of disc(s) 6, enters chamber 3 proximate to the outer perimeter 6b of disc(s) 6, and exits chamber 3 axially, as is the case with a Tesla turbine.

Where embodiments of the present invention comprise rotor 10a, 10b affixed to/ geared with hollow shaft 4, then it will be appreciated that rotation of hollow shaft 4 causes rotation of rotor 10a, 10b, and vice versa. Thus, when spent fluid imparts its momentum on rotor 10a, 10b after exiting chamber 3 via second hole(s) 7, any additional shaft power generated may be obtained via the hollow shaft 4 (or via the secondary shaft where applicable). Where embodiments of the present invention comprise rotor 10a, 10b affixed to an independently rotating secondary shaft, then it will be appreciated that the additional shaft power may be obtained via the secondary shaft instead of hollow shaft 4.

In light of the preceding discussion, it will be appreciated that the issue of turbulence generation within chamber 3 may be alleviated or mitigated by providing hollow shaft 4 containing one or more first hole(s) 5a, 5b, 5c in its elongate wall. This advantageous may similarly be realised in a case where turbomachine 1 does not carry out the energy conversion process via the boundary-layer effect, but rather via reaction forces.

Accordingly, and turning now to Figures 6A-6C, in embodiments of the present invention, each spacer 9 may span an entirety of a given planar surface in a radial direction thereof, wherein the one or more spacers 9 disposed on the given planar surface disc 6 are configured such that, when in use, the working fluid is directed along one or more curvilinear paths 9a extending in the radial direction of the given planar surface.

It can be seen in Figures 6A-6C that each spacer 9 may span the entirety of the distance between inner perimeter 6a and outer perimeter 6b of disc 6. As can be seen in Figure 6A, two spacers 9 are disposed on a given planar surface of disc 6, and are arranged (that is, shaped, sized, positioned, and/or oriented) such that curvilinear path 12 is formed between them. Similarly with each spacer 9, each curvilinear path 12 may span the entirety of the distance between inner perimeter 6a and outer perimeter 6b of disc 6. As can be seen from the dashed line in Figure 6A, curvilinear path 12 may curve as it extends from inner perimeter 6a to outer perimeter 6b.

Turning to Figure 6B, it can be seen that one spacer 9 may be used to form a single curvilinear path 12 on a given planar surface of disc 6. Turning to Figure 6C, it can be seen that a plurality of spacers 9 may be used to form a plurality of curvilinear paths 9a on the given planar surface of disc 6.

As will be appreciated, the previous discussion regarding the materials used in spacers 9, and the methods by which spacers 9 may be disposed on disc(s) 6 also apply here. Moreover, the spacers depicted in Figures 6A-6C may be similarly configured to reduce vibrations experienced by the discs and direct the working fluid when in use. Vibration reduction was discussed previously, and so will be omitted from here for the sake of brevity.

As will be appreciated, the curvilinear path(s) 9a formed on the planar surface(s) of disc(s) 6 may guide the working fluid from inner perimeter 6a to outer perimeter 6b. This guiding of the working fluid by curvilinear path(s) 9a may cause reaction forces to be generated on the radially-extending walls of spacers 9, thereby rotating disc(s) 6, that is, generating shaft power. For example, guiding/turning the working fluid from a radial direction (as it enters chamber 3 via first hole(s) 6) to a direction incorporating a non-zero azimuthal/circumferential component (as it exits chamber 3 via second hole(s) 7) results in a reaction force generated by the working fluid on the radially-extending walls of spacers 9. This reaction force may cause disc(s) 6 to rotate in a direction that is opposite to the azimuthal/circumferential component of the exiting (that is, spent) working fluid, thereby generating shaft power.

Conversely, this guiding of the working fluid by curvilinear path(s) 9a may be used to compress the working fluid. Using the examples of Figures 6A-6C, disc(s) 6 may be rotated clockwise, and the working fluid may enter chamber 3 via second hole(s) 7 in an anti-clockwise direction. As will be appreciated, the radially-extending walls of spacers 9 may generate a reaction force within the working fluid, thereby causing it to turn from this anti-clockwise direction to a radial direction as it exits chamber 3 via first hole(s) 5a, 5b, 5c. As is well-known by persons skilled in the art, this turning/guiding of the working fluid causes an enthalpy increase in the working fluid.

Turning now to Figure 7, it can be seen that spacers 9 may separate two of discs 6, or spacers 9a may separate a disc 6 from the interior wall of housing 2.

As with the previous "boundary-layer/Tesla" turbomachine 1 embodiments, the efficiency of the "reaction force" turbomachine 1 embodiments just described may be increased due to hollow shaft 4 and first hole(s) 6 providing a separate region/chamber for fluid undergoing axial-to-radial/radial-to-axial direction change, thereby reducing the amount of turbulence generated in chamber 3.

As with the previous boundary-layer/Tesla turbomachines 1, a thermofluid system may comprises one or more reaction force turbomachines 1. Indeed, the thermofluid system may comprise one or more boundary-layer/Tesla turbomachines 1 and/or one or more reaction force turbomachines 1.

When comprised within a thermofluid system, one or more reaction force turbomachines 1 may be configured to operate as a turbine. This is to say that one or more of reaction force turbomachines 1 may be configured such that, when in use: the working fluid enters chamber 3 via hollow shaft 4 and the first hole(s) 5a, 5b, 5c; the working fluid rotates the disc(s) 6 while travelling along curvilinear paths 12, thereby causing hollow shaft 4 to rotate; and the working fluid exits chamber 3 via the second hole(s) 7.

Alternatively or in addition, when comprised within a thermofluid system, one or more reaction force turbomachines 1 may be configured to operate as a compressor/pump. This is to say that one or more of reaction force turbomachines 1 may be configured such that, when in use: hollow shaft 4 rotates, thereby causing the disc(s) 6 to rotate, the working fluid enters chamber 3 via the second hole(s) 7, the rotation of disc(s) 6 forces the working fluid through curvilinear paths 12, thereby compressing the working fluid; and the compressed working fluid exits chamber 3 via first hole(s) 5a, 5b, 5c and hollow shaft 4.

The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. As will be understood by those skilled in the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting of the scope of the invention, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein, defines, in part, the scope of the foregoing claim terminology such that no inventive subject matter is dedicated to the public.

Claims (13)

1. CLAIMS1.A turbomachine, comprising: a housing enclosing a chamber; a hollow shaft rotatably mounted to the housing, wherein at least a first part of the hollow shaft is within the chamber, wherein the at least first part of the hollow shaft comprises one or more first holes in an elongate wall of the hollow shaft; one or more discs within the chamber and affixed to the at least first part of the hollow shaft; and one or more second holes within the housing, wherein the one or more second holes are configured such that, when in use, a working fluid enters or exits the chamber in a direction that is substantially orthogonal to the axis of the hollow shaft and is substantially tangential with respect to the direction of rotation of the discs.
2. 2. A turbomachine according to claim 1, wherein one or more of the discs each have one or more spacers disposed on one or both planar surfaces of the disc, wherein the one or more spacers are configured to reduce vibrations experienced by the discs and direct the working fluid when in use.
3. 3. A turbomachine according to claim 2, wherein at least one of the spacers is disposed proximate to an outer perimeter of the respective disc.
4. 4. A turbomachine according to claim 2, wherein each spacer spans an entirety of a given planar surface in a radial direction thereof, wherein the one or more spacers disposed on the given planar surface are configured such that, when in use, the working fluid is directed along one or more curvilinear paths extending in the radial direction of the given planar surface.
5. 5. A turbomachine according to any preceding claim, comprising a rotor within the hollow shaft.
6. 6. A turbomachine according to claim 5, wherein the rotor is affixed to a secondary shaft that is rotatably mounted to the hollow shaft.
7. 7. A thermofluid system comprising one or more turbomachines according to any one of claims 1 to 3, claim 5 or claim 6.
8. 8. A thermofluid system according to claim 7, wherein one or more of the turbomachines are configured such that, when in use: the hollow shaft rotates, thereby causing the discs to rotate, the working fluid enters the chamber via the hollow shaft and the first holes, the rotation of the discs compresses the working fluid due to the boundary-layer effect, and the compressed working fluid exits the chamber via the second holes.
9. 9. A thermofluid system according to claim 7 or claim 8, wherein one or more of the turbomachines are configured such that, when in use: the working fluid enters the chamber via the second holes, the working fluid rotates the discs due to the boundary-layer effect, thereby causing the hollow shaft to rotate, the working fluid exits the chamber via the first holes and the hollow shaft.
10. 10. A thermofluid system comprising one or more turbomachines according to any one of claims 4 to 6.
11. 11. A thermofluid system according to claim 10, wherein one or more of the turbomachines are configured such that, when in use: the working fluid enters the chamber via the hollow shaft and the first holes, the working fluid rotates the discs while travelling along the curvilinear paths, thereby causing the hollow shaft to rotate, and the working fluid exits the chamber via the second holes.
12. 12. A thermofluid system according to claim 10 or claim 11, wherein one or more of the turbomachines are configured such that, when in use: the hollow shaft rotates, thereby causing the discs to rotate, the working fluid enters the chamber via the second holes, the rotation of the discs forces the working fluid through the curvilinear paths, thereby compressing the working fluid, and the compressed working fluid exits the chamber via the first holes and the hollow shaft.
13. 13. A thermofluid system according to any one of claims 7 to 12, wherein the thermofluid system comprises one or more of: an engine, a refrigerator, a heat pump, hydroelectric turbines, pumps for transporting fluids, air conditioners, and ventilation systems.